ABSTRACT this dementia are permanent, worsen over


Alzheimer’s disease is
known to be the most common form of dementia, such as impaired judgment or
ability to make decisions, memory and changes in thinking
and other brain functions. Alzheimer’s disease accounts for 60 to 80 percent of
dementia cases. Approximately 200,000 Americans under
the age of 65 have younger-onset Alzheimer’s disease. In  the of 2001,  Dr. Tuszynski and his colleagues at the
University of California, initiated a clinical trial of nerve growth factor
(NGF) gene therapy in Alzheimer Disease , the first phase of an
experimental gene therapy protocol for Alzheimer’s disease. The main goal of
this clinical trial was to determine whether a nervous system growth factor
prevents or reduces cholinergic neuronal degeneration in patients with
Alzheimer disease. Ten patients with early Alzheimer disease were enrolled in
this clinical trial, underwent NGF gene therapy using ex vivo and in vivo gene transfer
with survival times ranging from 1 to 10 years after treatment. During the
clinical trial eight patients in the first phase 1 ex vivo trial and of two patients
in a subsequent phase one in vivo trial were examined. All ten patients were shown
a hypertrophy response to NGF gene therapy.



Alzheimer disease is an
inherit genetic mutation that can be passed from parent to child and
an aggressive brain disorder that is known to damage brain cells, causing
memory loss, changing behavior including some other brain functions 1.
Alzheimer is a types of dementia which is associated with brain cells damage;
in particular the brain region called Hippocampus which is the part of the
brain known to be in charge of memories. Note that this brain damage associated
with this dementia are permanent, worsen over time and cannot be reverse2.

though Alzheimer disease is known to be the cause of a rare combination of
genetic mutation. However, the genetic reason behind this disease is still a phenomena
and is still mostly unexplained. Although, the Genetic cause of the disease is
still unknown, the effect this disease have in human brain is very clear.  In a healthy human brain electrical process
take place that causes the human body to function normally. Inside of human
brain there are billions a neuron cells constantly communication with one another;
these healthy neurons are needed in order to function well. However Alzheimer
disease is known to disrupt this function and compromised this brain function
overtime which caused loss of memory. In Alzheimer disease abnormal Tau separate from the microtubule
causing them to fall apart. Which will soon cause fragments of the tau eventually later on would combine
and form a tangle inside the neurons and destroy the cells. As this process
continues neurons and other brain region would disconnect from each other and
they would completely stop communicate and dies. The brain would also shrank
and loses it permanent functions. Alzheimer become more dangerous as the
disease progress an early diagnosis is often a high change4.

progress very slowly most individual affected with Alzheimer are usually live
the disease for years before they start to notice symptoms of the disease which
make it very difficult to find a cure  The
people diagnoses with Alzheimer are usually between the ages of 30s to mid-60s this
is only represent a lower percentage of all the individuals. The reason why the
disease largely strikes at this specific age range is still a mystery for

Because of Alzheimer complication, so it questionable
that one or any drug intervention can successfully cure the disease. For over a
decade researches have been focus on improvement people to maintain mental
function and manage behavioral6.  Researches main goal to develop therapies
targeting specific genetic, molecular, and cellular mechanisms so that the
actual underlying cause of the disease can be stopped or prevented.

Nowadays researchers have reached to a point where they are able search beyond
treating symptoms and to reflect about addressing underlying disease processes7.
For a decade many ongoing therapeutic clinical trials have been developing and
testing by scientist and hope these therapeutic drugs might protect certain brain
cells and alleviated such as short term-memoryloss8.

In The year of 2001, Dr. Tuszynski and his
colleagues at the University of California, San Diego School of Medicine initiated
a first clinical trial at UC San Diego and the CNPRC,a gene therapy for an
adult neurodegenerative disorder . In April 2001, he delivered human nerve growth factor (NGF)
gene therapy that might prevent the neuronal degeneration and cell death
characteristic of Alzheimer’s disease9.

The main goal of this clinical trial was to
targets the cells that are located deep within part of the brain called cholinergic
system which supporting memory and cognitive function.  For over the course of this clinical trial, these
cells have been shown to react to NGF in primate studies. The researchers hope that
the NGF could inhibiting extensive loss of these cells that may slow
intellectual decline seen in Alzheimer’s patients9,10,11


A gene therapy that boosts nerve growth
factor (NGF) production in cholinergic neurons was safe and appeared to promote
neuronal growth in a small study of patients with early Alzheimer’s disease, researcher’s
reported12. The NGF protein was used for two main
reasons. First NGF is known to be a large and polar protein; therefore it is
too large to pass through the blood-brain barrier, making it difficult to
inject elsewhere13. Second, NGF broadly circulation throughout the brain
might causes adverse effects such as pain and weight loss. Research might
introduce the protein simply to surrounding degenerating neurons by precisely
injecting NGF into the brain14,15 .


“NGF gene therapy play a crucial role in
cognition to restore degenerated neurons and slow down the progression of
Alzheimer disease”


Targeted delivery of nerve growth factor (NGF)
has emerged as a potential therapy for Alzheimer’s disease due to its regenerative
effects on cholinergic neurons.

This research program tests the ability of
cells and growth factors to promote regeneration



of Alzeimer with NGF

In phase I of this trial, eight patients with
mild Alzheimer’s disease were enrolled in clinical trial over a time period
ranging from 2001 to 201116. These eight patients received ex vivo therapy to deliver the NGF gene
directly into their brains. Briefly, after the first injection skin biopsies
were obtained and examined from each patients, transduced to express human NGF using Moloney leukemia
viral (MLV) vectors 10,16. Which isolating connective tissue cells
called fibroblasts, genetically modifying them to express the NGF genes, and
then implanting the cells into the patients’ basal forebrain.  They used this strategy because NGF is too
large to cross the blood-brain barrier, and can stimulate other nerve cells,
leading to unwanted side-effects such as pain and weight loss 14,15.
The first part of the clinical finding  of the phase 1 ex vivo gene therapy have been reported , which involves inserting
NGF genes into skin fibroblasts and implanting those altered cells into their
brains. The second phase I clinical trial ten patients were enrolled in vivo gene therapy from 2005 to 2007, in
which an adeno-associated viral vector serotype 2 (AAV2) carrying NGF genes
were injected into their brains. The AAV2-NGF was used simply because it is less
expensive and some of the most dramatic results have been obtained has shown
promise for the treatment of inherited and degenerative diseases in a variety
of non-human primate brain for seven years 17,18.

Histology and Analyses


In order to determine whether degenerating
neurons in Alzheimer disease retain an ability to respond to a nervous system
growth factor delivered after disease onset. All surgical details regarding the
gene delivery have been reported, such as MRI scans of the ten patients in a
MRI compatible stereotaxic head frame in order to detect any brain target for
cell. During the ex vivo gene
delivery study five males and five females were enrolled where cells were
stereotaxically implanted into five sites equally spaced over the
rostral-to-caudal a total distance of approximately 12 mm. The NGF therapeutic
injections were precisely space at ~2.5mm intervals, indicated the distance
over which NGF spreads from gene delivery sites in non-human primates 10,17.

Statistical analysis

analyses were performed at an individual level using each patient’s own
baseline value as a control comparisons within the patients were made using
paired t-test with a significance criterion of P<0.05 where the test results were reported as mean ± SEM. The Patients were characteristics per ages, the mean age at diagnosis was 67.5 ± 2.2 years and the mean age at gene transfer was 69.3 ± 2.2 years. Patients survived a mean time period of 5.4 ± 1.0 years after gene transfer 19. Fluorescent Viability Determination Several sets tissues label were performed in order to evaluate the effect of NGF have in the brain. Firs, Nissl stain was performed to visualize the fibroblast grafts in ex vivo patients as well as the cellular morphology. NGF antibody: 1:500 dilution for fluorescence, 1:1000 dilution for light-level labeling. Then, p75 which detects the low-affinity NGF receptor and is expressed by NGF-responsive cholinergic neurons of the basal forebrain. Finally, c-fos, to assess activation of cell signaling classically related to NGF signaling.  And Phospho-tau immunolabeling to detect neurofibrillary degeneration20,21 . Antemortem Prediction of Braak stage The Braak stages of the patients within each control and treatment sample will be determined. These methods were used both in research and for the clinical diagnosis of these diseases and are obtained by performing an autopsy of the patient's brain. During the light level immunolabeling, sections were incubated 0·1M Sodium Periodiate for 20 min and rinsed in 0.1M of TBS, antibodies were also detected by incubating sections in 1.5 µg/ml biotinylated IgG. During the fluorescent immunolabeling section were sections were post-fixed in 2% paraformaldehyde and treated with 0.1M sodium borohydride for 30 min followed by 30 min in 0.5% Sudan black then Sections were incubated in primary antibodies for 72 hr at 4°C. Finally, p75 cells were measured using a stereological microscope, A counting frame of 300×300 µm with 1:4 sample ratio. The p75 cells bodies were performed in three patients that received unilateral transplantation of the autologous fibroblasts expressing NGF19,20,21. Pathological Evaluation of Brains During this clinical trial a pathological evaluation was performed in all study subjects. Signs Alzheimer disease were showed by ?-amyloid and tau in all patients, as well as NGF-treated subjects and control Alzheimer disease. POSSIBLE PITFALLS Biological response to NGF were reported in the largest parts if the patient's brain. Results cholinergic cell size in p75 labeled sections was measured in three subjects and received unilateral delivery of NGF. Cell hypertrophy which is a neuronal response to trophic stimulus was observed in brains of three patients undergoing the ex vivo NGF gene transfer21,23,24.  Further evidence, two patients that underwent AAV2-NGF in vivo gene transfer an activation of growth factor-induced canonical trophic signaling was also observed24. Significant   Alzheimer's disease-related deaths have increased over the past decades in every race, sex, and ethnicity category, however the good news is that even though this disease is progressive and cannot be stopped; much can be done to improve the quality of life for the person with Alzheimer.  The key to coping is a willingness to seek information and an openness to accept help and support from others. NGF is a new gene therapy administered to patients with established Alzheimer's disease results in classic trophic responses, characterized by axonal sprouting in all patients examined. Responses to NGF persist up to ten years after gene transfer. Subsets of patients examined for neuronal hypertrophy activation provide additional evidence for trophic activity. No adverse pathological effects are observed over this time period, supporting the safety and rationale for expanded clinical programs underway in Alzheimer's disease, Parkinson's disease and other neurological indications.